The present invention relates to a printing head ejecting ink drops to print (hereinafter referred to as xe2x80x9cink Jet headxe2x80x9d), and an ink jet recording apparatus using the same.
Recently ink jet recording apparatuses have come into wide use with the developments of printing in high picture quality and in colors. Of those developments, first, about the development of printing in high picture quality, the improvement of nozzle density in an ink jet head played a very large part. As the result of various investigation and development therefor, silicon, glass, photosensitive dry film, ceramics, etc. as well as metal and plastic used conventionally have come into use for an ink jet head in view of easiness in fine working, accuracy in working, process etc. In addition, to realize printing in high picture quality and in colors, investigation and development have been performed also upon ink. In order to optimize permeability or coloring properties of ink in the case where ink adheres to recording paper, or in order to improve shelf stability of ink for a long term, investigation and development have been performed also upon the components and compositions of ink. As a result, printing in vivid colors have been made able without generating mixing of different color inks adjacent to each other.
Thus, printing in high picture quality and in colors have been realized. However, it is considered that the material of an ink jet head may be dissolved in ink according the combination of the ink jet head material and the ink component. In that case, the component and composition of the ink or the material of the head is generally changed.
However, the following problems are pointed out when the material of the head is changed and replaced by another material which is not dissoluble in the ink.
First, the change of the material of the ink jet head causes sacrifices in accuracy of working and in easiness of fine working. As a result, lowering of nozzle density and hence lowering of printing quality may be caused. In addition, according to the material, it becomes necessary to change the process on a large scale.
Further, the component and composition of ink are adjusted so that the permeability and coloring properties of the ink on recording paper are optimized in order to improve the printing quality. In addition, the component and composition of ink are adjusted so as to improve the shelf stability of the ink for a long term. The change of the component and composition of ink causes lowering in one or some ink properties such as ink permeability and coloring in recording paper, printing quality, and long-term shelf stability.
It is therefore an object of the present invention to provide an ink jet head which is not corroded by ink and an ink jet recording apparatus using such an ink jet head.
In an ink jet head according to the present invention, an ink-resistant thin film is formed at least on the surface of each of diaphragms constituting pressure chambers each for giving pressure to ink to thereby eject the ink. The diaphragm which is a bottom plate of the; pressure chamber is easily affected by corrosion because the diaphragm is extremely thin. However, by forming the ink-resistant thin film in that portion, corrosion by ink can be prevented.
In addition, in the ink jet head according to the present invention, the ink-resistant thin film is formed in recess portions of a substrate for forming an ink reservoir for reserving the ink, orifices for guiding the ink from the ink reservoir into the pressure chambers, and the pressure chambers. The substrate is comparatively thin, so that the influence of corrosion on the substrate is large. However, corrosion by ink can be avoided by forming the ink-resistant thin film in the recess portions forming the ink reservoir, the orifices and the pressure chambers.
In addition, the ink-resistant thin film consists of Ti, a Ti compound, or Al2O3. The Ti compound consists of nitride or oxide. It has been confirmed that these ink-resistant thin films do not change even if the films contact with ink, and corrosion by ink can be avoided in the portion where the thin film is formed.
In addition, in an ink jet recording apparatus according to the present invention, any one of the abovementioned ink jet heads is attached thereto.
According to the present invention, therefore, even if the material of an ink jet head might be corroded by ink, it is not necessary to change the material of the ink jet head and the component and composition of the ink. In addition, the corrosion by ink can be prevented while avoiding lowering of printing quantity or a drastic change of the process due to the aforementioned change in the material of the ink jet head and in the component and composition of the ink.